The present invention relates to a handpiece and related apparatus for performing surgery and dentistry with a laser.
Applications of laser technology to medicine and dentistry have been suggested for well over a decade. Advances have been rapid, and laser devices are now commonly found, not only in operating rooms, but in the offices of physicians. Among the more widely used applications of laser technology in medicine is in the field of eye surgery.
Among the uses of lasers in the medical field are cutting, cauterizing, melting and ablating tissue. It has been recognized that to effect tissue, or other material to the greatest degree, one or more conditions must be met, including ( a ) the delivery of the laser energy in high powered pulses or with high continuous power; (b) the laser must be tuned to the extreme violet end of the spectrum where the photon absorption is high in organic substance; or (c) the laser must be tuned to the extreme infrared end of the spectrum where absorption of radiation by water, a major constituent of living tissue, is a factor. As is known, condition (a) functions through non-linear optical processes such as dielectric breakdown, which creates a finely localized absorption site because the resulting plasma is usually opaque to the laser beam. These noted conditions are extreme conditions and have resulted in the inability of some or all optical components to handle this extreme laser energy delivered.
In the care and treatment of eyes, it has been recognized that in some cases an eye may depart from a normal or "perfect" configuration, particularly in that the outer surface of the eye, the cornea, is not curved properly, but has some excessive steepness which cause kerataconus or myopia, resulting in impaired vision. Proposals have been made to correct this imperfection by changing the internal structure of the stroma layer of the cornea by the application of heat and/or radio frequency energy, but these proposals have had significant deficiencies. For example, Doss et al U.S. Pat. No. 4,326,529 attempts to achieve the correction of corneal irregularities by keratoplasty technique, in which the central stroma is heated with a radio frequency electrode probe, to break collagen crosslinks, to contract the collagen which is a part of the clear corneal medium. The method disclosed in Doss et al has the disadvantage that the heat deposition is not easily localized in the three-dimensional space of the cornea.
Roussell et al U.S. Pat. No. 4,409,979 provides apparatus for treating the human eye with laser radiation, and for viewing the site. Reflectors and prisms are provided to conduct light from a light source to the site, passing eccentric to the optical path; an image is conducted from the site to a viewing instrument, such as a microscope, centrally of the optical path. A beam from a laser is caused to strike the central part of a mirror which is movable between an operative position and a retracted position. In the operative position, the mirror directs the laser radiation to the site, generally along the optical path. In the retracted position, the mirror is removed from the optical path, permitting passage of the aforementioned light beam and observing beam. A weak laser is also provided, whose beam passes in a path eccentric to the optical path. A manually adjustable focussing lens is provided in the light paths to focus the light from the light source and the laser radiation. The arrangement presents a problem which requires the provision of a rotatable tube for housing beam splitters and reflectors which are part of the optical path of the light source beam, the observing beam, and the weak laser beam. Hence, manipulation of the rotatable tube and manual adjustment of the focussing lens are required to achieve the desired viewing and focussing, prior to the energization of the power laser and the moving of the mirror into operative position to direct the power laser beam to the site. The method of Roussell et al has the disadvantage that it cannot be moved with the freedom of a handpiece with six degrees of freedom. In addition, the method requires the intervention of an operator to establish the focal site of the laser energy delivery.
Muckerhide U.S. Pat. No. 4,316,467 discloses the use of a laser for treating birthmarks or lesions on the skin, in which control of the power or energy level of a laser is effected by receiving radiation reflected from the lesion by a fiberoptic bundle: a control circuit senses the intensity corresponding to the color intensity of the region to which the laser beam is directed and varies the energy of the laser.
Goldenberg U.S. Pat. No. 4,641,912 discloses an excimer laser system used for angioplasty, and includes a pair of optical fibers, one for obtaining an image of the atherosclerotic plaque to be ablated by the laser energy, a second optical fiber being provided for lasing the plaque. A video camera and monitor are utilized to acquire and display an image of the plaque.
Karlin et al U.S. Pat. No. 4,583,539 discloses a system for performing surgery on the eye using a CO.sub.2 laser source and an articulated arm structure, the laser energy being delivered through a probe which is connected to the articulated arm structure and which is insertable into an eye.
Kimura U.S. Pat. No. 4,266,549 discloses a laser scalpel including a probe through which light may be directed to illuminate the optical site: where a tumor is to be subjected to lasing, a picture or graphic representation may be obtained. An adaptor is provided at the tip of the probe to engage the tissue at or adjacent the tumor, to establish the distance of the focussing lens of the probe to the tumor to be laser.
Remy et al U.S. Pat. No. 4,289,378 discloses an apparatus for adjusting the focal point of a working laser beam onto a microscopic target region of a transparent biological object. Use is made of an auxiliary laser beam having a wavelength within the visible range, and through joint manual focussing of the laser beams, the location of focussing of the working beam at a particular locus at a desired depth within the transparent biological specimen is achieved.
The aforementioned disclosures, however, lack provision for a direct contact plano convex lens for the delivery of the laser energy to loci at very small ranges from the surfaces. They also lack provision for a contact lens surface to cover the cornea while the adjacent lower tissue is being irradiated and also to serve as a guide surface for hand held instruments. These limitations are overcome by the present invention as will be made evident below.
Among the patents disclosing a dental handpiece for directing laser energy to a tooth is Ota et al U.S. Pat. No. 4,503,853. In this patent, the handpiece includes a centrally located optical fiber through which the laser beam is passed to the tooth. The handpiece is provided at its distal end with a distance spacer to engage the tooth and provide a fixed spacing between the tooth and the end of the optical fiber to regulate the amount and strength of irradiation of laser beams from the laser source. Myers et al U.S. Pat. No. 4,521,194 discloses a method of removing incipient carious lesions and/or stains from teeth by the application of a laser beam from a source such as a yttrium-aluminum-garnet laser. In neither of these patents is there provision for autofocussing of the laser beam, nor is there a provision for viewing the site through the handpiece. These aforementioned apparatus also lack provision for the delivery of high peak power TEM(oo) laser mode radiation, as this radiation would normally destroy the fiber-optic delivery devices. For example, five millijoules Q-switched YAG laser pulses would destroy the single mode fiber-optic ends.